Import lib ring buffer into LTTng modules

[lttng-modules.git] / lib / ringbuffer / vatomic.h

diff --git a/lib/ringbuffer/vatomic.h b/lib/ringbuffer/vatomic.h
new file mode 100644 (file)
index 0000000..b944dd6
--- /dev/null
+++ b/lib/ringbuffer/vatomic.h
@@ -0,0 +1,85 @@
+#ifndef _LINUX_RING_BUFFER_VATOMIC_H
+#define _LINUX_RING_BUFFER_VATOMIC_H
+
+/*
+ * linux/ringbuffer/vatomic.h
+ *
+ * Copyright (C) 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Dual LGPL v2.1/GPL v2 license.
+ */
+
+#include <asm/atomic.h>
+#include <asm/local.h>
+
+/*
+ * Same data type (long) accessed differently depending on configuration.
+ * v field is for non-atomic access (protected by mutual exclusion).
+ * In the fast-path, the ring_buffer_config structure is constant, so the
+ * compiler can statically select the appropriate branch.
+ * local_t is used for per-cpu and per-thread buffers.
+ * atomic_long_t is used for globally shared buffers.
+ */
+union v_atomic {
+       local_t l;
+       atomic_long_t a;
+       long v;
+};
+
+static inline
+long v_read(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
+{
+       if (config->sync == RING_BUFFER_SYNC_PER_CPU)
+               return local_read(&v_a->l);
+       else
+               return atomic_long_read(&v_a->a);
+}
+
+static inline
+void v_set(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
+          long v)
+{
+       if (config->sync == RING_BUFFER_SYNC_PER_CPU)
+               local_set(&v_a->l, v);
+       else
+               atomic_long_set(&v_a->a, v);
+}
+
+static inline
+void v_add(const struct lib_ring_buffer_config *config, long v, union v_atomic *v_a)
+{
+       if (config->sync == RING_BUFFER_SYNC_PER_CPU)
+               local_add(v, &v_a->l);
+       else
+               atomic_long_add(v, &v_a->a);
+}
+
+static inline
+void v_inc(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
+{
+       if (config->sync == RING_BUFFER_SYNC_PER_CPU)
+               local_inc(&v_a->l);
+       else
+               atomic_long_inc(&v_a->a);
+}
+
+/*
+ * Non-atomic decrement. Only used by reader, apply to reader-owned subbuffer.
+ */
+static inline
+void _v_dec(const struct lib_ring_buffer_config *config, union v_atomic *v_a)
+{
+       --v_a->v;
+}
+
+static inline
+long v_cmpxchg(const struct lib_ring_buffer_config *config, union v_atomic *v_a,
+              long old, long _new)
+{
+       if (config->sync == RING_BUFFER_SYNC_PER_CPU)
+               return local_cmpxchg(&v_a->l, old, _new);
+       else
+               return atomic_long_cmpxchg(&v_a->a, old, _new);
+}
+
+#endif /* _LINUX_RING_BUFFER_VATOMIC_H */